An alkaline zinc secondary battery has a high energy density because the negative electrode comprises zinc. Moreover, zinc is favorably cheaper than a hydrogen storage alloy or the like. However, it has a high degree of solubility in an alkaline electrolyte. This leads to deformation of the negative electrode comprising zinc or to generation of dendrite, as charge/discharge cycles are carried out. These cause an internal short-circuit. And self-discharge of the alkaline zinc secondary battery is larger than that of any non-aqueous-type secondary battery.
In order to prevent internal short-circuit due to generation of the dendrite, proposed has been a technique using a separator comprising regenerated cellulose or polyvinyl alcohol or using a separator comprising a polyolefin micro-porous film which has been processed with a surfactant.
However, in a case where regenerated cellulose or polyvinyl alcohol is used for the separator, the alkaline electrolyte causes the separator to deteriorate. It is thus difficult to maintain the effect for a long time. Also in a case where the polyolefin micro-porous film was used for the separator, it cannot be said that the effect of preventing deformation of the negative electrode and internal short-circuit due to generation of the dendrite is sufficient. And there remains a challenge of inhibiting the self-discharge of the battery.